In HVDC (High Voltage Direct Current) applications, high voltage power converters are used for converting between the AC (Alternating Current) grid and DC (Direct Current). The conversion often occurs using a large number of converter cells. Converter cells are also used in other applications, such as medium voltage power converters.
US 2011/0267852 presents a voltage source converter having a series connection of switching assemblies, in which each switching assembly has an electrically conducting plate member carrying a plurality of semiconductor chips each having at least a semiconductor device of turn-off type and a free-wheeling diode connected in parallel therewith. Said chips are connected in parallel with each other by each being connected by at least one individual conductor member to a said plate member of an adjacent switching assembly of said series connection. Each switching assembly has a mechanical switch configured to be open under normal operation of the switching assembly and configured to enable connection of said plate member of the switching assembly to the plate member of an adjacent switching assembly for bypassing said semiconductor chips of the switching assembly to which the mechanical switch belongs in the case of occurrence of a short circuit current through a semiconductor chip of the switching assembly.
However, the solution of US 2011/0267852 may still be vulnerable to failure. Any improvement, no matter how small, in availability and reliability of power conversion applications in general, and mechanical bypass switches in particular, are of great benefit.